1. Field of the Invention
The invention relates to a device for piloting a craft—in particular a craft comprising at least one aerodynamic or hydrodynamic rudder, such as an aircraft or a ship.
2. Description of the Related Art
Throughout the text, and unless indicated otherwise, the term “piloting” and its derivative terms designate driving a craft by a human pilot who manoeuvres at least one piloting member such as a joystick, operating lever, control column, pedal, etc.
Traditionally, a device for piloting a craft comprises at least one piloting member connected to at least one driving member—in particular a rudder—of the craft, for controlling the position and/or movement thereof. A piloting member of this kind may be mounted and guided in rotation by means of at least one pivot connection about an axis in relation to an electromechanical support box. In the case for example of a sidestick for piloting an aircraft, the piloting member is mounted and guided in rotation by means of two pivot connections which are at a right angle and secant (forming a central point joint).
When the device for piloting is of the type called motorised, for each pivot connection of the piloting member the electromechanical support box comprises at least one actuating motor (in general a plurality of actuating motors to ensure redundancy in the case of an aircraft). An actuating motor of this kind in particular allows commands from a computer system for automatic pilot to be transmitted to the piloting member and/or a specific dynamic behaviour of the piloting member to be simulated in order to bring about a return to neutral and/or appropriate sensations (in particular sensations of muscular effort, simulations of friction or force feedback, assistance with movements, the combination of two piloting members on a single craft (pilot and copilot, etc.) which allow or facilitate piloting by a human pilot).
In the most common piloting devices, such as sidesticks for piloting aircraft, the actuating motors consist in electric motors, in particular torque motors or brushless three-phase rotary motors, which are coupled to the piloting member through the axis of the corresponding pivot connection, in most cases by way of a step-down geared transmission. Automatically switching sensors must be provided for controlling each phase of each motor in dependence on the position of the piloting member. Moreover, at least one return spring is coupled to the piloting member to return it to the neutral position in relation to the box. It is also possible for a damping element to be provided.
All these members, which must moreover be provided in multiple form for the sake of redundancy, are complex and subject to breakdown (taking into account in particular the large number of moving parts in contact with one another, which undergo friction and/or work fatigue), to gaps, and considerably increase the cost, weight and bulk of the piloting device.
Thus, WO 03/025394 describes a device for motorisation of a joystick, comprising a stator which includes an interior surface forming a spherical inner face, stator coils arranged at right angles, and a rotor which is movable along the interior surface of the stator and carries a plurality of magnets having a radial magnetic moment. A spherical architecture of this kind is particularly bulky and heavy, and is relatively ineffective from an electromagnetic point of view. Moreover, it is complex in its implementation.
DE 19501439 also describes a device for motorisation of a stick of the spherical type having electromagnetic architecture, in which the air gap forms a spherical inner face and the magnetic moment of the permanent magnets acting to pivot the stick about an axis of a pivot connection extends radially and not parallel to this axis. This device has the same disadvantages.
GB 2350170 describes a joystick device with force feedback comprising, for each pivot connection, an electromagnetic actuator comprising peripheral magnets having a radial magnetic moment in relation to the axis of the pivot connection, and a fixed armature forming an air gap in the shape of a portion of a cylinder about the axis of the pivot connection. This double-cylinder architecture does not allow a return torque to be obtained over a range of angular amplitude which is both large and controlled. Moreover, in this case too, this architecture results in considerable horizontal bulk.
GB 2412421 describes a method allowing a sensation of feedback force to be generated in a hydraulic actuation lever. In the first variant, a permanent magnet is associated with the handle and cooperates with one or the other of the electromagnetic coils to generate a magnetic force which is in opposition to the movement of the lever as a function of the variation in pressure of the fluid in the hydraulic circuit which is caused by the user moving the lever. The magnetic moment of the magnet is at a right angle to the axis of the pivot connection. Depending on the direction in which the current is applied to the coils, the magnet is attracted or repelled in one direction or the other. In the second variant, the electromagnetic architecture is of the spherical type. This document does not therefore enable the provision of a device in which an electromagnetic return is obtained in the absence of electrical supply or which moreover allows the above-mentioned problems to be solved.